FormatException on String to Int.ToList Conversion

Question

string aresultlist = File.ReadAllLines(data).ToString();
var bresultlist = aresultlist.Split().Select(s => Convert.ToInt32(s));
List<int> resultlist = bresultlist.ToList();

Can anyone help with the FormatException I keep getting on this block, "It's the datetime Format, take date first exception". It's a string read from a space delimited text file.

Why did you add `.ToString();` at the first line? How does your data look like? — Gilad Green, Sep 27 '17 at 06:36
Post sample of text. ReadAllLines() can cause big issues when parsing text files. You should read one line at a time using StreamReader(). I've been parsing text files for over 40 years and without seeing actual text I can't give good answer. — jdweng, Sep 27 '17 at 06:39
`ReadAllLines` returns string array... using `ToString` to a string array may produce unexpected results, i.e. resulting type instead of value. — Tetsuya Yamamoto, Sep 27 '17 at 06:40
It's not word wrapped here but:45 24 56 55 57 19 2 68 48 67 39 53 26 3 31 24 25 17 18 24 2 24 63 35 57 17 19 3 59 20 06 57 29 22 2 32 14 08 58 67 17 3 — Mariah Nelson, Sep 27 '17 at 06:40

score 2 · Answer 1 · answered Sep 27 '17 at 06:39

2

Try this:

  List<int> resultList = File
    .ReadLines(data)                      // you've got IEnumerable<string>
    .Select(line => line.Split())         // -/- IEnumerable<string[]>
    .Select(ietms => int.Parse(items[0])) // -/- IEnumerable<int> 
    .ToList();                            // finally, it's List<int>

I've assumed that it's the 1st item of the line which should be converted into int: int.Parse(items[0]), change 0 into the right index if required.

Try avoiding ReadAllLines in favor to ReadLines: you don't what all the file (which can be long) to be read into an array in one go

answered Sep 27 '17 at 06:39

Dmitry Bychenko

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I'd recommend using `TryParse` as in [this question](https://stackoverflow.com/q/4961675/6400526). And if using C# 7.0 [this answer](https://stackoverflow.com/a/46150189/6400526) – Gilad Green Sep 27 '17 at 06:42
@Gilad Green: `TryParse` is a *better choice*, but it may be *too complex* for the author of the question (the very reason I've put *two* `Select` one after one) – Dmitry Bychenko Sep 27 '17 at 06:46
I agree :) And that is why I didn't post an answer of my own including it (together with you managing to post before me :) I just added the comment so author can read about it in addition to your good explanatory answer – Gilad Green Sep 27 '17 at 06:48
This still returns FormatException. Thanks, it's late where I'm at so I'll check on this in a few hours. – Mariah Nelson Sep 27 '17 at 06:50
@Mariah Nelson: `FormatException` means that we're trying to parse -`int.Parse(items[0])` - a string that's *not an integer*, say `"bla-bla-bla"`. Could you, please, *share your file* (or peace of it)? – Dmitry Bychenko Sep 27 '17 at 06:56

Mong Zhu · Accepted Answer · 2017-09-27T06:48:44.810

the problem is that ReadAllLines returns a string[]. If you call ToString on such an object you get the namespace.classname as a string. So in your case:

System.String[]

splitting this string results definetely not a number. But in a string[] with on entry, namely:

System.String[]

If your file has only one line with the space delimited numbers, I would suggest to use File.ReadAllText. It will read the entire content of the file and return it as 1 string. This way you can use your code almost as it is.

string aresultlist = File.ReadAllText(data);
var bresultlist = aresultlist.Split().Select(s => Convert.ToInt32(s));
List<int> resultlist = bresultlist.ToList();

EDIT:

As suggested by Gilad Green you might have content in the file that cannot be parsed to a number and will throw an exception. To avoid this you can follow this example

As in Dimtry's answer here too: I'd recommend using `TryParse` as in [this question](https://stackoverflow.com/q/4961675/6400526). And if using C# 7.0 [this answer](https://stackoverflow.com/a/46150189/6400526) — Gilad Green, Sep 27 '17 at 06:46

FormatException on String to Int.ToList Conversion

2 Answers2